Novel technology enables eighth-brick line

The E48SX is a 48V-input single-output isolated DC/DC convertor that delivers up to 40A of output current in a true eighth-brick footprint and industry standard eighth-brick pinout.

The increasing demand for distributed power systems leads to a focus in the implementation of high efficiency, high power density, board mounted DC/DC convertors.

The task becomes even more challenging for low power high efficiency convertors, wherein high power density is required.

The lack of space requires a simple configuration with reduced number of parts in the power train section and the control as well.

Delta’s E48SX, 48V input, single output, isolated DC/DC convertor, delivers up to 40A of output current or 75W in a true eighth brick footprint (0.75in width, exactly half the size of a quarter brick) and industry standard eighth brick pinout.

To reach this performance the unit incorporates several new technologies in the area of topology, control magnetic and packaging.

The new topology used in this convertor is referred to as "constant voltage reset".

It is the result of the continuous quest for performance combined with simplicity.

The new topology combines all the advantages of the optimum reset while eliminating its limitations.

One of the drawbacks of the optimum reset circuit is its behaviour during transients wherein the duty cycle changes.

During transients, until the reset capacitor charges to its optimum level, the voltage across the switch may reach uncontrollable levels.

In this proprietary topology the voltage across the switch is constant regardless of the duty cycle and reacts to transients without any limitations.

In additional to this the implementation is very simple; it does not require any additional driving and timing circuits for the reset switch.

The reset switch is driven directly form the transformer by a driving winding and the reset voltage can be easily adjusted by a resistor divider.

To further improve the dynamic characteristics of the convertor performance the optocoupler was replaced with the magnetic feedback.

The magnetic feedback requires an additional magnetic element typically a small toroid mounted on a surface mounted header.

Though the size of these magnetic elements has decreased over the years, for the footprint of the E48SX, it will occupy approximately 5% of its surface.

This can be a major setback when the surface area it is a premium.

To eliminate this drawback this family of convertors is using another Delta proprietary technology claimed in the US Patent 6,414,578B1.

In this technology the signal is transferred through a magnetic element incorporated directly on the output choke core.

The winding of this signal transformer is placed in such a configuration that the magnetic field generated by the output winding it is not "seen by the signal transformer.

In this way on only one magnetic core it is used for two independent tasks.

Due to the fact that the signal winding is embedded into the multilayer PCB, the magnetic feedback element comes at actually no addition cost.

In addition to this the larger cross section of the output choke magnetic core reduces significantly the number of turns for the signal transformer and as a consequence the leakage inductance is reduced which reduces the delay of the signal.

In conclusion, using this technology Delta has implemented a signal transformer with very small delay time at no additional cost and practically zero footprint.

Using this proprietary technology the E48SX offers one of the best dynamic response in the industry.

For a load change from 20 to 30A with 1A/us slope the output voltage deviation it is less than 60mV.

To accommodate customers in noise sensitive applications, the E48SX offers not only one of the lowest ripple in the industry but also the capability of synchronisation with the existing standard pinout.

This is done by employing the trim pin for two functions.

The first function is for trimming and the second function for synchronisation.

This is possible because the trim function uses DC and very low frequency information while the synchronisation uses higher frequency information.

Using a frequency discriminator the trim function and the synchronisation function are using the same pin.

By synchronising the convertors in system applications the beating phenomenon can be avoided.

Another proprietary technology implemented in this convertor is referring to turn on under prebias conditions.

In the event wherein one of the convertors is turned on and there is an existing voltage on the output buss the convertor will not discharge it during the turn on transient.

This is a very good feature in many system applications.

This feature is accomplished through the memorisation of the output voltage and initiating the soft start from the existing initial conditions.

To further improve the efficiency some of the convertors from this family use another proprietary technology aimed at snubbing the synchronous rectifiers with minimum power loss.

This is accomplished by using an active snubber which activates the snubber as needed to reduce unnecessary charge flow and to increase the snubbing effectiveness.

This family of eighth-brick convertors uses five proprietary technologies in addition to two technologies referring to the packaging concept depicted in US Patent 5,990,776 and US patent 5,973,923.

This seven proprietary technologies makes these eight brick convertors the best in the industry in respect of power density, efficiency, system functionality, dynamic characteristics and low noise.

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